Investigation, development and verification of printed circuit board embedded air-core solenoid transformers

A new printed circuit board embedded air-core transformer/coupled inductor is proposed and presented. The transformer is intended for use in power converter applications operating at very high frequency between 30 MHz to 300 MHz. The transformer is based on two or more solenoid structures in different configurations. The different configurations are compared for usefulness as a transformer solution, and an analytical model of the inductive parameters for the most suitable configuration is derived for design purpose. The analytical model is verified by comparing calculations and measurements of prototypes. The analytical model shows good agreement with the measured results. The model can predict the inductive parameters of the transformer with a deviation range of approximately 3% to 22%. Lastly a prototype is used in a VHF converter to achieve a rise of 2.2% points in efficiency.